Abstract
A Depleted Monolithic Active Pixel Sensor (DMAPS) on thick film SOI technology is being extensively investigated as a possible candidate for the outer layers of the ATLAS Inner Tracker in the HL-LHC upgrade. Its radiation hardness to TID (Total Ionizing Dose) and the absence of back gate effect for a dose of up to 700 Mrad was proven. Its charge collection properties have been characterized with radioactive sources and with eTCT (edge Transient Current Technique) measurements for both, unirradiated and irradiated devices. This article presents the first test beam results on this DMAPS on thick film SOI technology. The charge collection properties, charge sharing between pixel cells, spatial resolution and tracking efficiency are presented as a function of the applied bias voltage and different selection criteria.
Highlights
At the edge of the pixel, about 30% of the deposited charge is shared with the neighbouring pixels
The device is 99.6% efficient at the central 80% of the pixel before irradiation, and test beam campaigns with irradiated devices will be performed in the coming months
Summary
The Device Under Test (DUT) is a DMAPS built on a thick film SOI CMOS technology using the XFAB 180 nm process [8]. The transistor’s bulk silicon is partially depleted (PD). This makes the technology promising against the radiation effects on the transistors and against the back gate effect observed in other SOI technologies [9, 10]. The process makes it possible to apply high bias voltages (up to 300 V), which are used to partially deplete the substrate. Additional grids surrounding each pixel to bias the sensor are included. The HV is applied from an outer guard ring, and in addition the chip includes additional grids surrounding each pixel. A detailed description of the chip has been described in several publications [6, 7, 12]
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